This proposal entails the provision of new, more effective and safe, organotin biocides. The synthesis, chemical and structural characterization, biocidal evaluation and some environmental fate analysis, of a new series of organotins, R3SnX and R2SnX2, that contain mixed functional groups will be performed. All presently known materials are homoleptic, i.e. all R groups are identical. Compounds with new R groups with specific properties (e.g. ionophore character, an important mechanistic property of organotins); systems with mixed R groups (active with less active substituents, e.g. ethyl and octyl groups); and oligonucleotide ligands will be targeted. Synthesis will involve procedures previous developed by the PI. Characterization will include multi-nuclear NMR, single crystal X-ray diffraction, and EXAFS; initial biocidal screening evaluation will involve direct testing against luminous bacteria. Synergistic activities of mixtures of organotins will be evaluated by the bacterial assay. Ionophoric properties with respect to both anion and cation transport will be determined. Promising materials will be further tested on more sophisticated systems via pre- arranged collaborative agreements. All appropriate, safety, handling, training programs and safeguards are in place. Organotins have widespread use against bacteria and fungi, in both agricultural crop production and human health arenas, including specific disease treatments and potential anti-cancer drugs. The properties of the various preparations are very dependent upon the R group present , thus the proposed research will have direct bearing upon the availability of new tools to fight disease and disease carrying pests. Recently it has been recognized that the use of organotins has been hampered by a clear lack of recent research in this field.